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Definition of word from the Merriam-Webster Online Dictionary with audio pronunciations, thesaurus, Word of the Day, and word games.

Vocabulary.com helps you learn new words, play games that improve your vocabulary, and explore language.

Comprehensive encyclopedia of mathematics with 13,000 detailed entries. Continually updated, extensively illustrated, and with interactive examples.

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The Khan Academy is a not-for-profit 501(c)(3) with the mission of providing a world-class education to anyone, anywhere. Despite being the work of o...

The Molecular Expressions website features hundreds of photomicrographs (photographs through the microscope) of everything from superconductors and hi...

Math explained in easy language, plus puzzles, games, quizzes, worksheets and a forum. For K-12 kids, teachers and parents.

The largest and most trusted free online thesaurus. Quickly find accurate and up-to-date synonyms, antonyms, and related words at Thesaurus.com. Synon...